1. Field of the Invention
This invention relates generally to the measurement of electric fields and more specifically to the use of the electro-optic effect to measure intensities of such fields.
2. Discussion of the Related Art
In various situations, it is desirable to measure the intensity of an electric field. One method for making such measurements involves using a bulk crystal having an electro-optic (EO) effect. In particular, a non-centrosymmetric crystal responds to an applied electric field via an EO effect. In the EO effect, application of an electric field changes a refractive index of a material. Due to the EO effect, light traveling through an electro-optically responsive material acquires a phase retardation proportional to the intensity of an applied electric field.
One conventional method for measuring the intensity of an electric field involves placing a bulk electro-optically responsive crystal in the electric field and directing a probing beam of light onto the bulk crystal. As the light traverses the bulk crystal, it accumulates a phase retardation that depends on the crystal's refractive index. Due to the EO effect, the value of the refractive index also depends on the intensity of the electric field. The method includes finding the intensity by measuring the phase retardation that the light accumulates while passing through the bulk crystal.
While some materials have a large EO effect, such materials are not always desirable for use in EO probes for measuring intensities of electric fields. In particular, such materials often have a large low-frequency dielectric constant. The large low-frequency dielectric constant increases the interaction between such materials and samples thereby making their use in EO measurements of field intensities invasive. Thus, materials with low or moderate EO coefficients may be preferable in EO probes for measuring the intensities of electric fields. Unfortunately, measuring the accumulated phase retardation is also more difficult when the probe is made with a material having a low or moderate EO effect.